Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 18 of 18 for “"air-cavity"”.
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Crossing the Air-Water Interface: Inspiration from Nature
… water is nearly a thousand times denser than air, transitioning between the two mediums is often associated with significant changes in force. Three topics with implications in water-entry are discussed, along with a fourth topic on water-exit. For a plunge-diving seabird, the first two stages …
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An Exploration of Transient Protection of Pressurized Pipelines using Air Valves
… having undulating profiles and containing air vacuum valves (AVVs) is systematically explored to characterize the critical high points where placing AVVs has the maximum influence on the resulting transient pressures. For this purpose, this work seeks to understand the principal function of …
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Study on single and double layers micro-perforated panel absorbers and optimal design by genetic algorithm
… perforation ratio, and the depth of the backed air cavity. The influence rule of the variation of the structure parameters on the absorption performance has been studied through numerical simulation with Matlab software. Compared with single structure, the double layers MPP absorber improve the …
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Fracture Morphologies in Particulate Suspensions
… shear-thickening suspensions subject to air injection. Wefirst highlight distinct modes of stress release in drying drops of colloidal suspensions. As water evaporates from a freshly deposited drop, a thin close-packed particle deposit forms at the edge of the drop and grows inward. Water …
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Design of a liquid embossing machine
… utilizes a PDMS stamp cast such that it seals an air cavity, which is then pressurized to slightly bow the stamp. The cavity is clear so alignment can be accomplished by optical feedback using a camera and microscope objective. The theory of liquid embossing is discussed. PDMS has a very high …
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Computations of fully nonlinear three-dimensional wave-body interactions
… surface impact of threedimensional objects, cavity dynamics in water entries, and coupled unstable motions of floating structures in waves. For the water impact problem, with the development of an adaptive jet flow treatment and an effective approach for accurately tracking water-body …
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Smart double panel with decentralised active damping units for the control of sound transmission
… thesis presents a comprehensive study of a smart aircraft double panel for active vibroacoustic control. The control of the double panel vibration is implemented using Multi-Input-Multi-Output (MIMO) decentralised velocity feedback loops. The loops are applied via an array of electrodynamic force …
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On falling spheres : the dynamics of water entry and descent along a flexible beam
… to characterizing the shape of the resulting air cavity in the limit where cavity collapse is strongly influenced by surface tension. A parameter study reveals the dependence of the cavity structure on the governing dimensionless groups. A theoretical description is developed to describe the …
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Dynamics of vacuum-sealed, double-leaf partitions
… transmitted acoustic energy by removing all the air between the two panels of the double partition. Therefore, the only remaining energy paths would be along the boundary and at the points where there are intermediate structural supports connecting the two panels. The eventual goal of the …
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Fiber Optic Sensors for On-Line, Real Time Power Transformer Health Monitoring
… for PD detection. By filling SF6 into the sensor air cavity of the extrinsic Fabry-Perot interferometer sensor, the last potential obstacle that prevents this kind of sensors from being installed inside transformers has been removed. The proposed acoustic sensor multiplexing system is stable and …
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Dynamics and Control of a Pressurized Optical Membranes
… vibration of optical membranes backed by an air cavity. This is achieved by using a centralized acoustic source in the cavity as the method of actuation. The acoustic actuation is of great interest since it does not mass load the membrane in the conventional way, as most methods of actuation …
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Design and numerical analysis of an unconventional surface-piercing propeller for improved performance at low and high speeds
… propellers operate in an encompassing vapor cavity, thereby averting these negative effects while substantially reducing drag on the blades. Surface-piercing propellers, operating under a similar concept as supercavitation, often achieve even greater efficiency by drawing in an air cavity …
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A Coupled Tire Structure-Acoustic Cavity Model
… shown that the vibration induced by the tire air cavity resonance is transmitted into the vehicle cabin and may be responsible for significant interior noise. The tire acoustic cavity is excited by the road surface through the contact patch on the rotating tire. The effect of the cavity …
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Feasibility study of a hybrid passive/active noise absorption system
… of minimizing the reflected wave in the airspace. The latter results in a match between the impedance in the air cavity and the impedance of a plane wave in air. This impedance-matching control approach was selected for the Passive/Active system because it meets the goal of optimum …
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An impulse framework for hydrodynamic force analysis : fish propulsion, water entry of spheres, and marine propellers
… into a basin of water and creates a sub-surface air cavity in place of a vortical wake, the vortex impulse is zero, and the force on the sphere is given by the pressure impulse component. Using data from high-speed imaging experiments, a semi-empirical numerical simulation is developed herein; …
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Active structural acoustic control of double panel systems including hierarchical control approaches
… by an advanced turboprop engine through the aircraft fuselage and the interior trim into the interior acoustic field which can be modeled as a double panel system. The system studied was a double panel model consisting of two rectangular, uniform, flat plates separated by a sealed air cavity, …
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Optimal design of sound absorbing systems with microperforated panels
… form of a thin panel with small holes, and an air backing may be one of the preferred solutions. These panels can be designed in many ways, and usually feature many small (sub-millimeter) holes and typically surface porosities on the order of 1 percent. The detailed acoustical properties of …
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Rendered rainscreen walls - cavity ventilation, ventilation drying and moisture-induced cladding deformation
… carrier boards are mounted on battens so that an air cavity is formed between the cladding and the backup wall structure. Provided that this cavity is open at the top and bottom, wind and thermal forces will create air circulation which means that moisture in the wall can be convectively removed. …